1. Field of the Invention
This invention relates to microprocessor systems. In particular, the invention relates to instruction set extension using 3-byte escape opcode values in an opcode field.
2. Description of Related Art
Microprocessor technology has evolved over the years at a fast rate. Advances in computer architecture and semiconductor technology have created many opportunities to design new processors. There are typically two options for designing new processors: (1) defining a completely new architecture, and (2) extending the current architecture to accommodate new features. Each option has both advantages and disadvantages. However, when a processor has captured a significant market segment, option (2) offers many attractive advantages. The main advantage of extending the current architecture is the compatibility with current and earlier models. The disadvantages include the problems of getting out of the constraints imposed by the earlier designs.
New processors involve new features in both hardware and software. A new processor based on existing design typically has an additional set of instructions that can take advantage of the new hardware design. However, extending an instruction set by adding a new set of instructions is a challenging problem because of the constraints in the encoding of the instructions. Therefore there is a need in the technology to provide an efficient method for extending an instruction set without increasing hardware complexity.